Answers
1

Isn't the clue in the final stanza? Frost tells you that a crop is a crop and asks you who's to tell when the harvest shall stop. Suddenly it is not just about leaves anymore. It seems to be that something can be very hard work, but yields an inconsequential result. I always liked the line where he says that "the mountains he raised, elude his embrace." It is very much like everything he has ever done or set in motion is now beyond him, yet it has never become momentous, but remains light.